EFFECTS OF ANTIMICROBIAL ADMINISTRATION ON THE EFFICACY OF EPIZOOTIC BOVINE ABORTION (EBA, FOOTHILL ABORTION) VACCINATION

<b>Project Methods</b><br> Beef cattle heifers from the same EBA-naïve herd, between 8-11 months and weighing between 600-900 lbs at enrollment, will be used for this study. Heifers will be randomly allocated into 5 groups, consisting of 20 animals each. Treatments will be followed by serial blood sampling for EBA serology, animal observations, and a second EBA vaccination. The Group treatment will be as follows:NO TREATMENT. Cattle will be inoculated with 2 ml vaccine diluent (PBS) and 6ml/100lbs body weight PBS subcutaneously to serve as a placebo for antibiotic treatment.EBA VACCINE ONLY. Cattle will be inoculated with 2 ml EBAA vaccine and 6ml/100lbs body weight PBS to serve as a placebo for antibiotic treatment.EBA VACCINE + OXYTETRACYCLINE. Cattle will be inoculated with 2 ml EBAA and oxytetracycline @ 20 mg/kg subcutaneously (volume dependent upon body wt).EBA VACCINE + FLORFENICOL: Cattle will be inoculated with 2 ml EBAA and florfenicol @ 40 mg/kg subcutaneously (volume dependent upon body wt).EBA VACCINE + TULATHROMYCIN: Cattle will be inoculated with 2 ml EBAA and tulathromycin @ 2.5 mg/kg subcutaneously (volume dependent upon body wt).Timeline:Day 0 – Early July 2021 – Blood collection for baseline EBA serology. Administer vaccine and antibiotics to appropriate treatment groups.Day 21 – Early August 2021 – Blood collection for EBA serologyDay 60 – September 2021 – Blood collection for EBA serology. 1st vaccination for Group 1, second vaccination for Groups 3, 4 and 5.Day 120 – November 2021 – Blood collection for EBA serology.Vaccination: Epizootic bovine abortion agent (EBAA; Hygieia Biological Laboratories, commercially available vaccine) will be administered as a single dose of 2ml SQ. Vaccination placebo (Group 1) will be 2ml Phosphate-Buffered Saline (PBS) SQ.Antibiotic treatments: One of three antibiotic treatments will be administered at the same time as the initial vaccination per label instructions.Blood will be collected from heifers four times (days 0, 21, 60, 120), with IFAT serology used to evaluate immunity of the heifers to P. abortibovis. Serology will be run in the Stott Laboratory at the UC Davis School of Veterinary Medicine with previously validated methods.Second vaccination: Cattle in Groups 1, 3, 4 and 5 will be vaccinated approximately 60 days after the initial treatment. This will be the first vaccination for cattle in Group 1 and the second vaccination for cattle in Groups 3, 4 and 5. It will be administered to ensure protection should antibiotics interfere with heifers mounting an effective immune response to the initial vaccination.Statistical Analysis:Sample Size = 20/group. Statistical powers = minimum size of 15 heifers/group (multiply 15 x 1.3 to allow for 30% of cattle being removed from analysis due to previous natural exposure to P. abortibovis). Justification of group size by statistical powers analysis: Two tailed ANOVA analysis comparing each treatment group to the positive control with a 95% confidence level (P value < 0.05); Power = 80%; 90% of Positive controls will seroconvert; 40% of antibiotic treated animals will seroconvert, while remaining 60% will not due to antibiotic interferenceData will be analyzed with a one-way ANOVA applied to serology data between groups and between time points. P-values for comparing all groups to one another computed using Tukey's multiple comparison test.